This invention relates to a clamshell type container or carton formed from a unitary blank of paperboard. Such cartons are characterized by a top lid or closure, often termed a crown, and a lower tray. The crown and tray have a common rear horizontal hinge joining their respective rear walls, with the tray having upwardly extending side walls, a front wall, and a rear wall. The crown has downwardly depending side walls, a front wall, and a rear wall. The crown is releasably latched to a closed position covering the tray by interengaging tongues or latches carried by the tray and crown. By virtue of the inherent resilience of paperboard, the tongues are easily engaged and disengaged. Typically, a warm fast food item such as a hamburger is placed into the tray and the crown closed for serving to a consumer.
While such cartons have met wide acceptance, there still is a need to improve their heat retention capability, as well as to improve their flexibility to permit easier stacking and easier conformation of the crown relative to the tray in the carton closed configuration.